KISS The PST etalon assembly is designed for an f10 input beam and to get optimum functionality/ performance the front lens of the etalon assembly should be placed at -200mm inside the prime focus of the telescope. That's it. (if you're using something like a SCT you can quickly determine if the eta...

Bob,
You mention resolution..
What is your typical plate scale, arcsec/pixel?
I find down here at the coast that working around 0.79 arcsec/pixel is about my limit. Using ED80 (80/600) for Ha and WL and stopped to f10 for CaK.

Interesting....
https://www.omegafilters.com/story/omega-artemis

Stu,
Did you get the chance to try the various filter combinations?
Ken

Raf,
A compromise would be to stop the scope to at least f10 and then use a reducer just before the camera to give you full disk coverage.
(With my ASI 1600MM on the ED80 I use either a x1.6 barlow or the very good x2.25 Baader Hyperion barlow to give me a slightly larger image on the sensor)

Raf,
Like Mark and others, I find the CaK filter gives better (repeatable) results when used at f10 (or greater).

I respect anyone who considers building a SHG!
I'm finding that there's always a "twist" in the final design! Finding suitable sized gratings for instance.....

Andrew,
The two profiles show the bandwidth shift when the filter assembly was slightly moved.
It’s the same filter, just different tilts.

RAF,
As far as I can tell, the Lunt CaK filter doesn’t involve an etalon solution, just multi-coated filter elements.
The Quark obviously (I think may have a micra solid etalon) is different.
What f ratio scope are you using??

Thanks everyone for the comments/ feedback. Using the spectrograph to measure filters/ etalons etc. removes the subjectiveness of assessing the capabilities of your filter(s). My usual spectrograph (R=10000) is locked up on the C11 for ProAm work at the moment. Bit difficult at the moment, but if I ...

Frank,
The combination of the cut-off wavelengths and "double stacking" contributes to the reduced bandwidth.
The tilt (sag of the filter assembly) moved the central wavelength (CWL) towards the blue.

Just checked the Lunt CaK filter the 18mm is over $1000 and rated for 2.4 A (or less???)

Limited test... The only available spectrograph was a Spectra-L200 with a 1200 l/mm grating, this gave a dispersion of 0.23A Using the normal set up with the ED80 stopped down to f10. The bandwidth of the DIY filter is very close to 1.0 A Bad news: due to the filter assembly "sagging" due to the add...

Three Omega Bob filters (yes, I know some users say they are rubbish quality!), a Baader Blue CCD filter as an upfront erf and fitted with the #1 "yellow" filter from a PST Cak scope. Certainly not cheap!!! I think the Lunt CaK filter is probably more cost effective, but.....I think the DIY has a ti...

Between cloud....
I'm in the process of measuring the bandwidth and central wavelength of the DIY CaK filter I use.
Based on the images I've uploaded previously, any bets on the outcome????

Frank,
Well done!
Very impressive outcome.

Frank,
Well done!
Very impressive outcome.

Stu, sorry to high-jack the thread..... Alexandra, Interesting question... My CaK DIY (three Omega filters + PST Cak "yellow") always seem to give "sharper" contrast features compared to others. I'm using the ASI 1600MM and sampling at 0.79 arcsec/pixel. My seeing is pretty average to bad..... I use...

Franco,
Well done mate!
Nice presentation

Ken

Franco,
Well done mate!
Nice presentation

Ken

Thanks everyone!
Your feedback is appreciated.

Imaging on the 6th Sept after days of cloud and wind....
I've seen "shadows" of possible proms with my DIY CaK filter - but today there was no ambiguity!
Definitely a CaK prom.
ED80/x2.25 Baader/ ASI 1600

Alexandra,
Even with the ERF the PST mod would act as an aperture stop and bring the TEC to a100mm f10 system.

Charon,
I have used an original SM60 mounted on an ED80 successfully for many years.
IMHO opinion it works better than the current SM60II scope.

Mark, et al,
As recently reported the tuning of the PST etalon is by pressure, distorting the plates.
Any additional knobs on the orange ring are there to “equalize” this pressure nothing to do with tilt.

I’d say they are dumped gold tubes from PST mods. This tube is replaced by a larger objective scope. Check the condition of the front objective, if it’s gold colored then it has the original ERF coated version which has failed, and no longer usable. These are redundant and off no real use. They can’...